can: m_can: m_can_tx_handler(): fix use after free of skb

commit 2e8e79c416aae1de224c0f1860f2e3350fa171f8 upstream.

can_put_echo_skb() will clone skb then free the skb. Move the
can_put_echo_skb() for the m_can version 3.0.x directly before the
start of the xmit in hardware, similar to the 3.1.x branch.

Fixes: 80646733f11c ("can: m_can: update to support CAN FD features")
Link: https://lore.kernel.org/all/20220317081305.739554-1-mkl@pengutronix.de
Cc: stable@vger.kernel.org
Reported-by: Hangyu Hua <hbh25y@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 19a7e4adb9338d945490fb68117221a23ba3529b..19a19a7b7deb87b3a73895f044f4cd0e387650bb 100644 (file)
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1491,8 +1491,6 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
                                         M_CAN_FIFO_DATA(i / 4),
                                         *(u32 *)(cf->data + i));
 
-               can_put_echo_skb(skb, dev, 0);
-
                if (cdev->can.ctrlmode & CAN_CTRLMODE_FD) {
                        cccr = m_can_read(cdev, M_CAN_CCCR);
                        cccr &= ~(CCCR_CMR_MASK << CCCR_CMR_SHIFT);
@@ -1509,6 +1507,9 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
                        m_can_write(cdev, M_CAN_CCCR, cccr);
                }
                m_can_write(cdev, M_CAN_TXBTIE, 0x1);
+
+               can_put_echo_skb(skb, dev, 0);
+
                m_can_write(cdev, M_CAN_TXBAR, 0x1);
                /* End of xmit function for version 3.0.x */
        } else {